At Seikomodder.com, we provide expert guidance on selecting the right tools for every aspect of watch modification. One of the most critical tools in any modder’s kit is the watch caseback tool. Whether you’re doing a battery change, movement swap, or full Seiko mod, you’ll need to safely open and close the caseback to access the movement. These tools are designed to break or recreate the water-resistant seal, which protects the internals of the watch from dust and moisture.
What Does a Watch Caseback Tool Do? – Seiko Mod Tools
Most Seiko watches feature screw-down casebacks with six notches on the outer edge. Watch caseback tools s are made to fit securely into these notches, allowing you to twist the caseback open without slipping, scratching the case, or damaging the seal. Just as important, they help you close the caseback properly, ensuring the water-resistance is restored after any work inside the watch.
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Handheld Watch Caseback Tool – Seiko Mod Tools
Handheld tools are the most common and accessible option for modders. They come in several styles:
Two Pin Watch Caseback Tools
- Bergeon 7662 – A high-quality Swiss tool with adjustable pins, suitable for various case sizes.
- Horotec 07.014 – Another precision-made tool, offering strong grip and good stability.
Three Pin Watch Caseback Tools
Large (Wide) Watch Caseback Tools – Large or wide-jaw caseback tools, like the Bergeon 2819-08 (Maxi Jaxi) or the high-quality generic version from a respected 75-year-old watchmaker’s parts supplier, are built for handling oversized casebacks that standard tools can’t grip. While neither option is cheap, they’re built to last a lifetime — and in the context of Seiko modding, they probably will. The price and size maybe a little over kill for most Seiko modders so these tools are rarely, if ever, needed. But if you do come across the occasional outlier, having one of these in your drawer can be a real time-saver.
Generic Watch Caseback Tools – 2 & 3 Pin
- Generic 2-pin or 3-pin tools – These basic tools are more than adequate for most Seiko watches. The three-pin version offers better balance and a lower chance of slipping. The quality of these tools varies, for just a few poinds more you can purchase a far better quality tool, an example below
Any Good for beginners?
For beginners, a generic 2- or 3-pin opener is a solid and affordable choice. These will work on most Seikos, and paired with care and patience, they’ll get the job done just fine.
To make using these tools safer and more effective, it’s a good idea to use a case vice—a device that holds the watch still while you apply turning force. We’ll cover case vices in more detail in another article, but they’re definitely worth having and can be purchased inexpensively on their own or within a budget tool kit.
Rubber Ball – Watch Caseback Tool
An even easier option for beginners is a rubber ball-style caseback opener like the Bergeon 8008, 8001, 8015 & others. These soft, tacky rubber balls grip the back of the case without using metal pins, so there’s no risk of scratching the case. Bergeon have playfully made these like Pool balls. They’re perfect for watches that aren’t tightly sealed against an old dry gasket, and can often handle opening and closing the back without any additional tools. They’re also great for resealing the case without damaging the gasket or misaligning the threads which does happen with cheap case parts.
If you’re only modifying one or two watches, this might be the simplest and safest tool to start with,
Bench-Mounted Openers
For those doing frequent mods or working on stubborn casebacks, bench-mounted openers offer a more robust solution. Models like the Bergeon 5700 and Horotec 07.360 come with a built-in vice and a large turning wheel, allowing for stable, even pressure using both hands. These tools are excellent for resealing cases securely while minimizing the chance of damage. There are also Chinese-made copies of the Bergeon 5700 available, which provide similar functionality at a lower cost—ideal for serious hobbyists looking to save.
Budget Friendly Options (Clones)
Chinese Clone of the Bergeon 5700 – Having used both the genuine Bergeon 5700 and its clone, the differences are clear. The original offers smoother action, a stronger return spring, and far better alignment and finish. However, the clone still does the job and represents great value for new modders looking to keep costs down. In our experience, Bergeon replacement parts do fit the clone we have here — at least with the model we’ve had running reliably in the workshop for the past 3–4 years — which adds extra flexibility and long-term potential to this budget-friendly option. Its locking mechanism helps keep dies stable during use, which significantly reduces the risk of slipping or scratching casebacks. This press is fast becoming a staple for watchmakers, modders, and hobbyists alike, thanks to its excellent value proposition and practical reliability.
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Don’t Forget the Keys – Watch Caseback Tool
For bench-mounted tools or bar-style tools, you may need interchangeable caseback keys. These keys fit specific case sizes and slot patterns. While Seiko casebacks tend to follow a common six-slot design suitable for the Jaxi type tool other brands or custom watches may require different keys. The right key ensures you apply pressure evenly and avoid stripping the slots or damaging the caseback. With the availability of submariner, explorer, OP and datejust cases the requirement for a set of rolex keys will likely become apparent for anyone venturing into building custom watches with these case. Although the ball mentioned above does a great job these keys with a minimum of a locking bar gives a modder piece of mind that the caseback is sealed tight.
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Wrap-Up – Watch Caseback Tools
Whether you’re new to modding or well into the hobby, having the right watch caseback tool is crucial. If you’re just starting out, a rubber ball or basic three-pin opener will do the job for most Seiko models without costing much. As you get deeper into watch modding or work on a wider range of timepieces, investing in more precise tools like the Bergeon 7662, Horotec 07.014, or a bench-mounted opener will help you work more safely and efficiently.
And remember: opening the case is only half the job—closing it properly is just as important to preserve the water-resistant seal and keep your watch running smoothly.
Honest Review- Watch Caseback Tools
In our workshop, we’ve put a wide variety of caseback tools through real-world use. For handheld tools, the generic 2- and 3-pin openers definitely feel budget—but they still get the job done. They rattle more than you’d expect, but for basic Seiko modding, especially when paired with a caseback ball, they offer good value. We also use two higher-quality eBay-sourced openers (wide and standard size), and they’re noticeably better built. When it comes to rubber balls, we’ve tested genuine Bergeon models (8001, 8007, 8008, etc.), as well as the clone 8008 and generic blue and red balls. The clones feel harder and don’t grip as well, while the genuine Bergeons consistently perform well. The blue ball actually outperforms the 8008 clone thanks to its softer material. Just note that all of them need to be re-inflated occasionally, with the generic ones losing pressure more quickly. For bench-mounted tools, we’ve used two clones of the Bergeon 5700 and, after upgrading the springs (the stock ones are too soft), they work great. While the genuine 5700 is smoother and better aligned, the clones are more than capable with a few tweaks—and offer excellent value for regular modders.
Stay tuned for our next tool guide on case vices—and check out the rest of our Seiko mod Basic Tool Kit to build your perfect modding setup.
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